Abstract: The semicontinuous enrichment of isotopes and the variation of the total enrichment of the isotope species to be enriched while approaching the steady state of the band are studied. The experiments show the variation of the total enrichment vs displacement follows the expression derived by one of the authors:  In the enriching process, for a band of a given length, the total enrichment depends only on the displacement distance and the total enrichment of the steady band, not on the isochrone shape. Therefore, the semicontinuous enrichment process can be predicted by knowledge of the variation of the total enrichment vs displacement. By repeating the displacing-cutting-enjecting-displacing cycle important quantities of the more riched mixture will be produced. This manner may be used for refining of isotope concentrated feed.